Consists of all the nerve cells. It is the body's speed, electrochemical communication system

Central Nervous System (CNS)

brain and spinal cord

Peripheral nervous system (PNS)

the sensory and motor neurons that connect the CNS to the rest of the body

Nerves

consist of neural "cable"containing many axons. They are part of the PNS and connect muscles, glands, and sense organs to the CNS

Neurons

Basic unit of the nervous system. Allow communication between the brain and sensory organs, internal organs, and muscles.

Sensory Neurons (Afferent)

Conduct sensory impulses from eyes, ears, and other sense organs to the CNS.

Motor Neurons(Efferent)

Conduct motor impulse out from the CNS to muscles and organs

Interneurons

Connect one neuron to an other

Cell Body

the cell's life support center

Dendrites

receive messages from other cells

Axons

passes messages away fro the cell body to other neurons, muscles, or glands

Neural impulse

action potential electrical signal traveling down teh axon

Terminal branches of axon

from junction with other cells

Myelin sheath

covers the axon of some neurons and helps speed neural impulses

How neurons communicate signals

Electrochemical Process

Electrical-conduction of impulse within neuron

Chemical- transmission of impulse between neurons

Conduction of Impulse

Threshold

each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity(threshold) the neurons fires and action potential i.e. electrical impulse passes down the axon with constant intensity

Conduction of impulse

re polarization

once fires, resting potential returns

Conduction of impulse

Absolute Refractory Period

brief period of time after firing when neuron won't fire

Conduction of impulse

all or none law

Neuron either firing with full intensity of resting (resting potential.) Increases in intensity of stimulation don't cause stronger impulse but lead to more rapid firing or to activation of more neurons.

conduction of impulse

relative refractory period

period of time after firing when neuron will only fire in response to strong stimulation

Transmission of message

Synapse

small gap between axon of one neuron and the dendrite of another through which chemical messages are transmitted

transmission of message

Axon terminal

The end of the axon. Contains synaptic vesicles.

transmission of message

Action potential

causes vesicle to open and release neurotransmitters(chemicals that have specific different shapes) which travel across synapse and bind to matching receptor sites on receiving neuron, thereby influencing it to generate an action potential

Reuptake

Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake.

This process applies the brakes on neurotransmitter action.

Lock and key Mechanism

Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism

How some drugs work

Agonist neurotransmitter

the agonist molecule excites. It is similar enough in structure to the neurotransmitter molecule that it mimics its effects on the receiving neuron.

Morphine- mimics the actions of endorphins by stimulating receptors in brain areas involved in mood and pain sensations

how some drugs work

antagonist neurotransmitter

this molecule inhibits. it has a structure similar enough to the neurotransmitter to occupy its receptor site and block its action, but not similar enough to stimulate the receptor.

- Hormones travel longer distances and their effects slower & more prolonged than neurotransmitters (some chemicals can be both.)

hypothalamus

brain region controlling the pituitary gland

thyroid gland

affects metabolism

adrenal glands

sit above kidneys, secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress.

testis

secretes male sex hormones

ovary

secretes female hormones

pituitary gland

secretes many different hormones, some of which affect other glands

regulates growth.

parathyroid

help regulate teh level of calcium in the blood

pancreas

regulates the level of sugar in the blood

The spinal cord and reflexes

1. information is carried from skin receptors along a sensory neuron to the spinal cord. From here it is passes via interneurons to motor neurons that lead to muscles in the hand and arm

2. this reflex involves or spinal cord, the hand jerks away from candle flame even before informing it about the event has reached the point of causing the experience of pain

Computerized Axial Tomography (CT or CAT scan)

a series of x-ray photographs taken from different angles and combined by computer into a 3d composite representation of the brain

used to detect tumors and stroke damage

CTs have been useful in identifying schizophrenia patients. In these patients' brains: the ventricles (fluid- filled open spaces), are significantly larger than in normal individuals, which means that they have less brain tissue to process cognitive functions.

Instead of a flat, two-dimensional X-ray picture, CT scanners produce a series of successive images. Taken as the patient, lying down, moves through a scanning ring, these "slices" can be combined to create the illusion of a 3-D image.

Detects such things as tumors & stroke damage.

Electroencephalogram(EEG)

- An amplified recording of the electrical waves sweeping across the brain’s surface, measured by electrodes placed on the scalp.

- Brain activity is plotted as a line (Brain wave).

- Used in sleep and other kinds of brain research.

MRI Scan Magnetic Resonance Imaging

- Uses magnetic fields and radio waves to produce computer-generated images that distinguish among different types of brain tissue.

- Allows us to see structures within the brain - Used for diagnosing tumors and epilepsy.

FMR

measures brain function. It tracks brain activity by monitoring changes in how much oxygen the brain cells are consuming. That serves as an indicator of how much blood is flowing to various brain regions, which in turn shows how active the neurons are.

•Typically, fMR subjects are placed in an MRI machine and asked to perform a mental task such as remembering and repeating words presented to them.

Postion Emission tomography PET

- A visual display of brain metabolic activity.

- Detects where a radioactive form of glucose travels while the brain performs a given task.